Study of Trend of Chemical and Microbial Changes of Rainbow Trout (Oncorhynchus Mykiss) to Determine the its Optimum Shelf-Life During Storage in Refrigerator Temperature (4°C)

Nowadays، importance of keeping and presentation of fresh fish، with regard to consumer preference for fresh fish rather than frozen fish، is increasing. So، determination of fish shelf-life، to find its consumption time، due to high perishability of fish، is important. This study was aimed to investigate the process of spoil changes and determining the shelf-life of rainbow trout (Oncorhynchus mykiss) fillet during storage period in refrigerator (4°C). For this purpose، rainbow trout fillets were kept in refrigerator for 18 days and the changes of free fatty acids (FFA)، tiobarbitoric acid (TBA)، total volatile bases nitrogen (TVB-N)، total viable count (TVC) and sensory evaluations were assessed. The results showed that the quantity of chemical indices increased during storage period. With regard to the standard quantity of TBA، TVB-N and TVC and also sensory evaluation of panel group، the samples were out of the specified standard on 5 day. Considering of correlation between chemical and microbial indices with total acceptability showed that the most precise indices for shelf-life determination of rainbow trout fillet is TVC (6 log cfu/g) indicator and TVB-N (about 25 mg in 100 g fillet). Accordingly، rainbow trout fillet can be kept in refrigerator for 5 days.